A hollow-core fiber based optofluidic chip for rapid immunofluorescence detection with simultaneous enhancement of sensitivity and enrichment efficiency

Although conventional ELISA is highly sensitive, its intricate workflow, significant background interference and dependence on laboratory infrastructure severely restrict its use for on-site testing. Lateral-flow assays (LFAs) are simple and portable, yet the numerous manual steps and inability to deliver truly quantitative results lead to inadequate sensitivity and poor reliability, failing to meet clinical requirements. Therefore, there is an urgent need for an immunological method that is both highly sensitive and simple to perform. Here, we propose an all-fiber optofluidic immunosensor based on a hollow-core fiber (HCF) that integrates the entire assay onto a single microfluidic chip. A standard fiber is inserted into the HCF for direct light coupling, and the gap between the two fibers serves as the sample inlet, eliminating external pumps and tubing. The inner wall of the HCF can be functionalized, providing an extremely high surface-to-volume ratio; the long, confined microchannel shortens analyte diffusion distances and prolongs residence time, markedly improving antibody-capture efficiency and reducing enrichment duration. Coaxial propagation of both light and the sample inside the HCF strengthens light-matter interaction and enhances fluorescence collection efficiency. Without any pre-incubation, quantitative detection of influenza A antigen is completed within 10 min, achieving a limit of detection of 2.41 pg mL^-1. The limit of detection and assay time of this method are both lower than those of many conventional lateral flow immunoassay cases, and the method exhibits excellent reproducibility and specificity. The proposed HCF microfluidic chip successfully breaks the conventional sensitivity-<i>versus</i>-speed trade-off, offering a promising solution for rapid point-of-care clinical diagnostics.